diff -r 14ad8e2a4abe -r 003c41edc5f5 mercurial/changelog.py
--- a/mercurial/changelog.py	Thu Sep 22 21:51:58 2016 +0900
+++ b/mercurial/changelog.py	Thu Sep 22 21:51:59 2016 +0900
@@ -382,9 +382,9 @@
             tmpname = self.indexfile + ".a"
             nfile = self.opener.open(tmpname)
             nfile.close()
-            self.opener.rename(tmpname, self.indexfile)
+            self.opener.rename(tmpname, self.indexfile, checkambig=True)
         elif self._delaybuf:
-            fp = self.opener(self.indexfile, 'a')
+            fp = self.opener(self.indexfile, 'a', checkambig=True)
             fp.write("".join(self._delaybuf))
             fp.close()
             self._delaybuf = None